Tryptophan Pathway Abnormalities in a Murine Model of Hereditary Glaucoma

A Review on the Role and Function of Cinnabarinic Acid, a "Forgotten" Metabolite of the Kynurenine Pathway

In the human body, the majority of tryptophan is metabolized through the kynurenine pathway. This consists of several metabolites collectively called the kynurenines and includes, among others, kynurenic acid, L-kynurenine, or quinolinic acid. The wealth of metabolites, as well as the associated molecular targets and biological pathways, bring about a situation wherein even a slight imbalance in the kynurenine levels, both in the periphery and central nervous system, have broad consequences regarding general health. Cinnabarinic acid (CA) is the least known trace kynurenine, and its physiological and pathological roles are not widely understood. Some studies, however, indicate that it might be neuroprotective. Information on its hepatoprotective properties have also emerged, although these are pioneering studies and need to be replicated. Therefore, in this review, I aim to present and critically discuss the current knowledge on CA and its role in physiological and pathological settings to guide future studies.

Efficacy of Continuous-Wave Transscleral Cyclophotocoagulation Post-Pars Plana Vitrectomy in Glaucoma Patients: A Retrospective Study from Poland

BACKGROUND Glaucoma, a vision-threatening condition, results from optic nerve damage and affects millions of people worldwide. Often asymptomatic, it is hereditary, with risk factors like hypertension, diabetes, and steroid use. Despite its link with intraocular pressure (IOP), not everyone with high IOP develops glaucoma. After pars plana vitrectomy (PPV), patients face increased IOP risks. Traditional treatment includes pharmacotherapy, and, when ineffective, surgical interventions. Continuous-wave transscleral cyclophotocoagulation (CW-TSCPC) is an alternative for refractory glaucoma but can have complications. Our study compares the efficacy and safety of CW-TSCPC after PPV. MATERIAL AND METHODS The study group consisted of 18 patients diagnosed with glaucoma who underwent the CW-TSCP procedure as the first-choice therapy after conservative treatment of glaucoma proved ineffective. The comparison group consisted of 12 patients who underwent the CW-TSCP procedure after conservative drug treatment and in whom surgical treatment of glaucoma had been unsuccessful. All patients had inadequate control of IOP after PPV. RESULTS Study and comparison group patients showed a decrease in IOP during the follow-up, independent of the type of endotamponade used (P<0.05). When the indication for PPV was retinal detachment hemorrhage into the vitreous chamber, a significant decrease in IOP between 0 days and 180 days was only found in the study group (P<0.05). In contrast, when the indication for PPV was the state after uveitis or proliferative diabetic retinopathy, a significant decrease in IOP was found at 180 days in the study and comparison groups (P<0.05). CONCLUSIONS The analysis showed that the CW-TSCPC procedure can be recommended as the first-choice invasive treatment in patients with increased IOP after PPV.

Association between dietary calcium, potassium, and magnesium consumption and glaucoma

BACKGROUND

Calcium (Ca), potassium (K) and magnesium (Mg) may be involved in the occurrence and development of glaucoma by influencing the retinal oxidative stress and regulate blood pressure. However, epidemiological opinions on dietary intake of macroelement related to glaucoma are inconsistent. Herein, this study aims to explore the association between dietary Ca, K, and Mg consumption and glaucoma.

METHODS

Data of 7,042 adults aged ≥40 years old who received the glaucoma examinations were extracted from the National Health and Nutrition Examination Survey (NHANES) database from 2005 to 2008 in this cross-sectional study. Univariate and multivariate logistic regression were used to explore the association between dietary Ca, K, and Mg intake and glaucoma with the odd ratios (ORs) and 95% confidence intervals (CIs). We also investigated this relationship in individuals of different age, with/without hypertension and visual field defect (VFD).

RESULTS

There were 502 (8.11%) participants had glaucoma. After adjusted for covariables, we found that enough dietary Ca consumption was related to a decreased risk of glaucoma [OR = 0.59, 95%CI: (0.42-0.81)], whether in persons with/without hypertension (all P<0.05). In particular, dietary K intake may be a potential protect factor for glaucoma in non-hypertension populations [OR = 0.47, 95%CI: (0.22-0.99), P = 0.049]. Additionally, hypertension/non-hypertension persons who aged <65 years old or with/without VFD should all pay attention to the enough dietary supplement of Ca, K, and Mg according to their own circumstances.

CONCLUSION

Enough dietary Ca, K, and Mg consumption may be potential protect factors of glaucoma that could provide some dietary reference for developing targeted glaucoma prevention and control measures.

Aryl hydrocarbon receptor dependent anti-inflammation and neuroprotective effects of tryptophan metabolites on retinal ischemia/reperfusion injury

Glaucoma is the major cause of irreversible blindness in the world characterized by progressive retinal neurodegeneration, in which local inflammation in retina is involved in persistent loss of retinal ganglion cells (RGCs). In order to explore whether aryl hydrocarbon receptor (AhR) and its agonists tryptophan metabolites are involved in the development of glaucoma, we collected serum and retinas from non-glaucoma controls and patients with glaucoma. Results showed altered serum tryptophan metabolism and reduced retinal AhR expression in glaucoma patients. We also showed intraperitoneally injection of tryptophan metabolite 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) down-regulated retinal local inflammation and protected RGC apoptosis from retinal ischemia/reperfusion (IR) injury via AhR activation. We further revealed that ITE could inhibit inflammation in BV2 microglia and alleviate the neurotoxicity of microglial conditioned medium to RGCs under IR. Finally, we illustrated the possible mechanism that ITE limited ERK and NFκB dependent microglial inflammation. In summary, these findings suggest the critical role of tryptophan metabolism and retinal AhR signaling in modulating local inflammation mediated by microglia in glaucoma, and provide a novel avenue to targeting the intrinsically altered AhR signaling resulted from disturbed tryptophan metabolism for glaucoma treatment.

Testing the eligibility of glaucoma patients for potential gene therapy among a clinic population

PURPOSE

Glaucoma patients who deteriorate despite standard treatment may benefit from novel gene therapies. Key inclusion criteria for a glaucoma gene therapy trial were devised. A retrospective chart review in a glaucoma clinic population was conducted. Feasibility of gene therapy inclusion criteria and factors associated with progression and fast progression < -1 decibels/year (dB/y) were evaluated.

METHODS

Three hundred and seventy-four primary open-angle glaucoma patients all of whom had performed at least five Swedish interactive threshold algorithm standard visual fields within a 58-month period. Two definitions were applied to characterize visual field progression rate using Guided Progression Analysis for an individual patient based on A, the eye with the greatest visual field loss, or B, the eye with the most rapid progression rate.

RESULTS

Mean rate of visual field progression was  -0.50 dB/y (Definition A) and  -0.64 dB/y (Definition B). 19.0% (A) and 21.9% (B) of eyes, 71 (A) and 82 (B) eyes, were 'fast progressors' (<  -1 dB/y). 37 (A) and 43 (B) eyes met the putative gene therapy inclusion criteria (≥ 50 years; mean deviation ≤  -4 to ≥  -12 or ≤  -20 dB, progression rate between  -1 and  -4 dB/y). Beta blockers (Odds ratio (OR) with 95% Confidence Intervals (CI): 2.84 (1.39-5.80); p = 0.004) (A), (OR (95%CI): 2.48 (1.30-4.75); p = 0.006) (B) and alpha agonists (OR (95%CI): 2.18 (1.14-4.17); p = 0.02) (A), (OR (95%CI) 2.00 (1.08-3.73); p = 0.028) (B) were significantly associated with fast progression.

CONCLUSION

A substantial proportion (10%) of patients in this clinic population would meet recommended gene therapy inclusion criteria.

Simultaneous quantification of 26 NAD-related metabolites in plasma, blood, and liver tissue using UHPLC-MS/MS

Nicotinamide adenine dinucleotide (NAD) is a key metabolic intermediate found in all cells and involved in numerous cellular functions. Perturbances in the NAD metabolome are linked to various diseases such as diabetes and schizophrenia, and to congenital malformations and recurrent miscarriage. Mouse models are central to the investigation of these and other NAD-related conditions because mice can be readily genetically modified and treated with diets with altered concentrations of NAD precursors. Simultaneous quantification of as many metabolites of the NAD metabolome as possible is required to understand which pathways are affected in these disease conditions and what are the functional consequences. Here, we report the development of a fit-for-purpose method to simultaneously quantify 26 NAD-related metabolites and creatinine in mouse plasma, whole blood, and liver tissue using ultra-high performance liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS). The included metabolites represent dietary precursors, intermediates, enzymatic cofactors, and excretion products. Sample preparation was optimized for each matrix and included 21 isotope-labeled internal standards. The method reached adequate precision and accuracy for the intended context of use of exploratory pathway-related biomarker discovery in mouse models. The method was tested by determining metabolite concentrations in mice fed a special diet with defined precursor content.

The Effect of Ocular Perfusion Pressure on Retinal Thickness in Young People with Presumed Systemic Hypotension

Low ocular perfusion pressure (OPP) may increase the risk of optic neuropathy. This study investigated the effects of OPP on the ganglion cell complex (GCC) and optic nerve head-retinal nerve fibre layer (ONH-RNFL) thickness in presumed systemic hypotensives (PSH). Fifteen participants with PSH and 14 controls underwent automated sphygmomanometry and Icare tonometry to calculate OPP: mean OPP (MOPP), systolic OPP (SOPP), and diastolic OPP (DOPP). ONH-RNFL and macula GCC thickness were evaluated using the Optovue iVue optical coherence tomographer. Statistical analysis comprised independent t-tests, the Mann-Whitney U test and binary logistic regression analysis. There was no significant difference when comparing ONH-RNFL and macula GCC thickness between both groups. Increased MOPP (OR = 0.51; 95% CI: 0.27-0.97; p = 0.039) and SOPP (OR = 0.79; 95% CI: 0.64-0.98; p = 0.035) were significantly associated with a decreased risk of reductions in GCC total thickness. Increased SOPP (OR = 0.11; 95% CI: 0.01-0.89; p = 0.027) was significantly associated with a decreased risk of reductions in the average ONH-RNFL thickness. The study found no significant retinal thickness changes in PSH's, in comparison to the controls. The study established that, by increasing MOPP and SOPP, there was a decreased risk of reductions in the total GCC thickness and average ONH-RNFL thickness. Higher SOPP may decrease the possibility of retinal thinning of the GCC and ONH-RNFL. However, higher MOPP may decrease the odds of thinning of the GCC before ONH-RNFL changes.

Neuroprotection in Glaucoma: NAD+/NADH Redox State as a Potential Biomarker and Therapeutic Target

Glaucoma is the leading cause of irreversible blindness worldwide. Its prevalence and incidence increase exponentially with age and the level of intraocular pressure (IOP). IOP reduction is currently the only therapeutic modality shown to slow glaucoma progression. However, patients still lose vision despite best treatment, suggesting that other factors confer susceptibility. Several studies indicate that mitochondrial function may underlie both susceptibility and resistance to developing glaucoma. Mitochondria meet high energy demand, in the form of ATP, that is required for the maintenance of optimum retinal ganglion cell (RGC) function. Reduced nicotinamide adenine dinucleotide (NAD⁺) levels have been closely correlated to mitochondrial dysfunction and have been implicated in several neurodegenerative diseases including glaucoma. NAD⁺ is at the centre of various metabolic reactions culminating in ATP production—essential for RGC function. In this review we present various pathways that influence the NAD⁺(H) redox state, affecting mitochondrial function and making RGCs susceptible to degeneration. Such disruptions of the NAD⁺(H) redox state are generalised and not solely induced in RGCs because of high IOP. This places the NAD⁺(H) redox state as a potential systemic biomarker for glaucoma susceptibility and progression; a hypothesis which may be tested in clinical trials and then translated to clinical practice.

Influence of Trace Elements on Neurodegenerative Diseases of The Eye-The Glaucoma Model

Glaucoma is a heterogeneous group of chronic neurodegenerative disorders characterized by a relatively selective, progressive damage to the retinal ganglion cells (RGCs) and their axons, which leads to axon loss and visual field alterations. To date, many studies have shown the role of various elements, mainly metals, in maintaining the balance of prooxidative and antioxidative processes, regulation of fluid and ion flow through cell membranes of the ocular tissues. Based on the earlier and current research results, their relationship with the development and progression of glaucoma seems obvious and is increasingly appreciated. In this review, we aimed to summarize the current evidence on the role of trace elements in the pathogenesis and prevention of glaucomatous diseases. Special attention is also paid to the genetic background associated with glaucoma-related abnormalities of physiological processes that regulate or involve the ions of elements considered as trace elements necessary for the functioning of the cells.